Finally, we can cross out the density in each term of the equation, since it’s not changing.

最后，我们可以划掉等式每一项中的密度， 因为它没有变化。

Finally, we can cross out the density in each term of the equation, since it's not changing.

最后，我们可以从 等式的两边，因为它不是一个变量。